This plugin shows thin lines at indentation levels. Think it as a lightweight re-implementation of "indentLine" or such.
$ git clone https://github.com/matveyt/vim-guidedspace ~/.vim/pack/manual/start/vim-guidedspace
For Vim make sure you have
filetype plugin indent on
syntax on
in your vimrc in this order. For Neovim it's a builtin default.
Also read :help GuidedSpace
.